Waterproof fiberboard



Patented Apr. 15,19 24.

UNITED STATES PATENT OFFICE.-

ALBERT L. CLAPP, F DANVERS, MASSACHUSETTS, ASSIGNOR T0 BECKWITH MANU-FACTURING COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MAINE.

WATERPROOF FIBERIBOARD.

No Drawing.

To all whom it may concern:

Be it. known that I. ALBERT L. CLAPP, a citizen of the United States,residing at Danvers, in the county of Essex and State of Massachusetts,have invented new and useful Improvements in \Vaterproof Fiberboard, ofwhich the following is a specification.

This invention has for its object the utilization of material for whichthere has been no commercial use, namely, box toe waste, i. e, thescraps left after cutting box-toe blanks from a sheet of fibrousmaterial containing bitumens, resins, waxes, or other thermo-plasticstiffening agents, alone or in admixture. It has hitherto been thepractice, in the manufacture of box-toes, toform a sheet' of fibrousmaterial, such. as fielt formed either on a felting machine or a papermachine, to impregnate or saturate the sheet with a thermo-plasticcompound, adapted to be softened upon the application of moderate heat,and then to ,cut the boxtoe blanks of appropriate size and shape fromthe sheet, and insome cases to subject such blanks to a calenderingoperation. Due

' flammability of the solvent, the cost of re-' to the shape of theblanks, there is neces sarily' a wastage of the sheet material due tothe formation of scraps and cuttings, for which no use has heretoforebeen found. Attempt has been made by the use of a solvent to extract thevaluable gums, resins or other stiffening agents from'the waste scrapmaterial, but this has proved commer clally to possess little value, dueto the incovery, and the other necessary operations which are expensive.Then, again, the stiffening agent usually comprises-several ingredientsblended together to impart to the box-toe the desired characteristics,and these ingredients may be varied acording to. thevarying coststhereof. Among these thermo-plastic materials are montan and carnaubawax, common or blown asphalt, rosin and copal-resin, I resin soaps,drying oils, etc., some or all of which, included by the termthermo-plastic compound, are used in varying proportions, to produce acompound or mixture which will readily penetrate the fibrous sheet,soften at a moderate temperature, while not affected by body or solarheat, set rapidly when cold, and impart stiffness and rigidity to themolded toe box. Such compounds are usually characterized Applicationfiled December a, 1922. Serial No. 605,721.

y though they have no sharp or critical melt ing and solidifying points.7

I have found that it is possible to use such waste box-toe material inthe production of a water-repellent fiberboard for a number of uses inthe arts, wherein both the fibrous material and the thermo-plasticcompound possess great value. Ordinarily the proportion ofthermo-plastic compound to fiber by weight is relatively large, andalthough additional fibrous material is supplied for the manufacture offiberboard, the thermoplastic compound is suflicient, when coalesced, inthe sheet, to furnish the necessary or desirable water-proof orwater-repellent qualities.

After much experimentation, I have found that it is possible todisintegrate the boxtoe waste by grinding it while dry in a suitablegrinding machine, such as an Abbe grinder. It is desirable from time totime to throw a handful of talc into the grinder to prevent thethermo-plastic compound from sticking to the knives. When disintegratedto a relatively fine dry state, the material is now ready for use.

I place'in a beating engine a quantity of cellulose fiber, such, forexample, as chemical wood pulp, or sulphite, or sulphate screenings,waste kraft or manilla paper, or other paper making stock, together withsuflicient a relatively short melting point lag,

ably subject the stock to a prolonged beating sufficient to produce afairly hydrated or slow stock. Then while continuing the beating'operation, I add (say four parts) a quantity of the disintegratedbox-toe waste, and thoroughly mix it with the hydrated paper stock untila homogeneous pulpy mass is produced. The stock is now sheeted by anyapproved papermachine, such as a wet machine, a multi-cylinder machine,or a Fourdrinier machine. When first formed and dried, it is relativelyporous, but I now subject the sheet to both heat and pressure, as by.the use of heated rolls, by which the thermo-plastic compound, which isdistributed throughout the fibersof the sheet, is fiuxed or softened andcoalesced into a state of continuity throughout the sheet, so as toenclose the fibers and protect them against the access of moisture. Inthe foregoing example, the mucilaginous hydrate on thecellulose fibersand fibrillaa is sufiicient toretain in the pulp those particles of thethermoplastic compound which were freed from adherence to the fibers bythe grinding operation, during the forming of the sheet and the removalof water therefrom, but the ex- 40 parts cellulosic stock, and 80 to (50parts box-toe Waste, by dry weight.

In many cases I regard it as desirable to use some additional device forfixing the thermo-plastic particles on the fibers to prevent their wastewith the white water, since I may also thereby reduce the length of thebeating and decrease the extent of colloidal hydration. To this end, Iadd to the stock in the beater and incorporate therein a suitable sizingcompoufid, which I then precipitate by a suitable precipitating agent,so that the free particles of thermo-plastic compound are coagulated,carried down and fixed upon the fibers. I employ a rosin size, orsilicate of soda, or both, as the sizing compound, and precipitate thesame with alum or other suitable precipitant.

As indicating the proportions which may be used, the following willserve as examples, though it will be understood that these proportionsmay be greatly increased.

Example Example '11.

. 70 parts box-toe waste 30 parts sulphite pulp 10 partsrosm size 2parts silicate of soda 15 parts alum and pigments or dyes.

Example 111.

2040 parts sulphite pulp, beaten from to 4 hours 80-60 parts box-toewaste.

The final product forms, after subjection to heat and pressure, a harddense highl water-repellent or water-proof fiberboar which may bemolded, and which may be used in the manufacture ofi trunks, containers,automobile flooring, etc., and which lends itself to many other uses inthe arts.

What I claim is:

1. A process of making fiberboard which comprises disintegrating box-toewaste having a thermo-plastic compound incorporated therein, forming anaqueous pulp of said disintegrated material together with cellulosicmaterial, and sheeting said pulp on a paper machine.

2. A process of makin fiberboard which comprises disintegrating ioxtoewaste having a thermo-plastic compound incorporated therein, whilemaintaining said waste in a dry state, pulping said disintegratedmaterial together with cellulosic material and water, and forming saidpulp into a sheet.

3. A process of makin fiberboard which comprises disintegrating %OX-t0waste having a thermo-plastic compound incorporated therein, whilemaintaining said waste in a dry state, pulping said disintegratedmaterial together with cellulosic material and water, forming said pulpinto a sheet, and

subjecting such sheet to heat and pressure to flux and cause thecoalescence of the thermoplastic compound.

4. A process of makin fiberboard which comprises disintegrating %)0Xt08waste having a thermo-plastic compound incorporated therein, beatingcellulosic material with water to form a pulp, incorporating thedisintegrated waste material together witha sizing compound in saidpulp, adding a precipitating agent, and then sheeting the resultantpulpy mass on a paper machine.

5. A process of makin comprises disintegrating ox-toe waste having athermo-plastic compound incorporated therein, beating cellulosicmaterial with water to form a pulp, incorporating the disintegratedwaste material together with a sizing compound in said pulp, adding-aprecipitating agent, sheeting the resultant pulpy mass on a papermachine, and finally y heat and ressure fluxing the particles ofthermo-plastic compound incorporated in the sheet. v

6. A water-repellant fiberboard comprising cellulosic material, anddisintegrated fibrous box:toe waste having a thermo-plastic compoundincorporated therein, all with the fibers in felted relation andprotected by the said thermo-plastic com ound.

fiberboard which a In testimony whereof I ave aflixed my 7 signature.

ALBERT L. CLAPP.

